1. Field Of The Invention
The present invention relates to a door apparatus with a release assembly, and more particularly to a fire-rated, rolling steel door with a release assembly which allows an operator to easily and quickly drop test the door to determine if it will operate properly during a fire.
2. Description Of The Prior Art
A fire-rated, rolling steel door assembly typically includes a rolling steel curtain member, a drum for supporting the curtain, a counterbalance system for overcoming the weight of the curtain, and a drop or release assembly that allows an operator to drop the curtain from a raised position to determine if the curtain member will drop properly during a fire. The release assembly should allow quick and easy operation to encourage period "drop-testing" of the assembly.
Many prior fire-rated, rolling steel door assemblies utilize a torsion spring counterbalance mechanism (much like the mechanism used in standard non-rated fire doors) to overcome the weight of the door and thus allow an operator to open and close it. To drop-test these doors, one merely releases part of the turns or the winds in the torsion spring, allowing the door to drop. A system of oscillating governors, fluid clutch mechanisms, or centrifugal clutches control the descent of the door. These systems vary in size, construction and complexity depending on the door size.
The prior door assemblies described above suffer a number of disadvantages. They require skilled operators and special tools to drop test and reset them. To reset these prior assemblies, an operator usually must use a ladder, scaffold, or hoist and expose himself or herself to the danger of falling. Finally, in relatively large door assemblies, the components of the drop mechanism (e.g., oscillating governors) must withstand a great deal of stress and large impact forces. Thus, the manufacturers must use large amounts of costly material to construct them and thus avoid component failure.
The assembly of the present invention avoids the disadvantages of the prior art devices. It includes a counterbalance system that accurately balances the door throughout its descent. This system allows the use of components of reduced size to control the door during its descent; and it greatly minimizes the stresses and impact forces attributable to the drop mechanisms of the prior door assemblies. Moreover, the assembly of this invention allows the use of a standard size governor for all door sizes. It is a simple system which avoids complex procedures and provides smooth operation and reliable performance.